JP6380482B2 - Electrodeposition coating method and cleaning water removal promotion device for electrodeposition coating line - Google Patents

Description

  The present invention relates to an electrodeposition coating method and an apparatus for promoting cleaning water removal in an electrodeposition coating line.

  Electrodeposition coating is widely used for corrosion protection of metal products such as automobile bodies. In this electrodeposition coating, securing the throwing power when the object to be coated has a complicated structure has been a problem. For example, in the case of an automobile body, not only the outer plate portion (outer surface) exposed to the outside but also the inner plate not exposed to the outside such as the interior of the vehicle interior, the engine room, or the inside of the bag-shaped portion It is desired that an electrodeposition coating film having a predetermined thickness is also formed on the portion (inner side surface). However, the inner plate portion of the automobile body is farther from the counter electrode (electrode) and has a lower current density than the outer plate portion, so that the paint hardly deposits and the coating film tends to be thinner. On the other hand, if a coating film having a required thickness is formed on the inner plate portion, the coating thickness of the outer plate portion becomes excessive.

  As a countermeasure against the throwing power problem, for example, as described in Patent Document 1, there is known a method (double coating) in which an electrodeposition paint is adhered to an object to be coated in two steps. The first electrodeposition coating is formed on the outer surface of the coating after the coating is immersed in the first electrodeposition bath to form a first electrodeposition coating film, and the coating is washed with water. The coating film is heat-flowed, and then the object to be coated is immersed in a second electrodeposition tank to form a second electrodeposition coating film. After washing the object to be coated, the first electrodeposition coating film and the second electrodeposition film are washed. This is a method in which the coated film is cured by heating. According to this method, for example, in the case of an automobile body, a hole through which hydrogen gas generated during electrodeposition can be formed in the first electrodeposition coating film of the outer plate portion is blocked by heat flow. The electric resistance of the outer plate portion is increased. As a result, the inner plate portion is easily energized, and a large amount of the second electrodeposition coating material adheres to the inner plate portion. Therefore, an electrodeposition coating film having a desired thickness can be formed on the inner plate portion while suppressing an increase in the coating thickness of the outer plate portion.

Japanese Patent Laid-Open No. 10-8291

  However, as a result of the inventor's experiment and research on the double coat, the first electrodeposition coating film was washed with water, and the washing water for washing was partially left. It has been found that the following problems occur when the electrodeposition coating is heated.

  FIG. 8A shows a state in which cleaning water 103 is attached to the first electrodeposition coating film 102 on the article 101. In this state, when the first electrodeposition coating film 102 is heat-flowed, as shown in FIG. 8B, the wetted portion of the first electrodeposition coating film 102 with the cleaning water 103 and the cleaning water are not attached. A recess 104 is formed at the boundary with the dry part. This is because the temperature of the dry portion of the first electrodeposition coating film 102 rises quickly due to heating during the heat flow, but the temperature of the wetted portion of the cleaning water 103 increases until the cleaning water 103 evaporates. This is because of delay. That is, a temperature difference occurs between the wet part and the dry part, and as a result, a difference occurs in the volume shrinkage between the two parts. Since the volume shrinkage of the dry part is larger than the wet part, when the position of the boundary hardly moves, the first electrodeposition coating film of the boundary part is pulled toward the dry part, and FIG. As shown in C), a relatively deep recess 104 is formed at a portion corresponding to the boundary.

  When the second electrodeposition coating is performed in a state in which such a recess 104 is formed, the portion that has become the recess 104 has a lower electrical resistance than its surroundings, so that the electrodeposition paint is likely to adhere. As a result, as shown in FIG. 8D, the second electrodeposition coating film 105 corresponding to the boundary between the wet part and the dry part is locally thickened. That is, the convex part 106 is produced. In such a case, even if the intermediate coating and the top coating are performed, smoothness is not obtained on the coated surface, or unevenness of the electrodeposition coating film as the undercoat appears on the appearance through the intermediate coating and the top coating, and the appearance is poor. Become.

  As a result, the surface of the object to be coated, such as the roof of an automobile body, is particularly liable to become partially stagnant due to surface tension without flowing down the washing water. Become prominent.

  Therefore, the present invention prevents the electrodeposition coating from being uneven in the double coating.

  In order to solve the above-mentioned problem, the present invention forcibly removes or reduces the washing water adhering to the coating material after washing the coating material on which the first electrodeposition coating film is formed and before the heat flow. I did it.

In the electrodeposition coating method disclosed herein, a DC voltage is applied between an object to be coated and a counter electrode in a first electrodeposition tank to form a first electrodeposition coating film on the object to be coated. After washing with water, the electrical resistance of the first electrodeposition coating film formed at a site close to the counter electrode of the article to be coated is higher than the electrical resistance of the first electrodeposition coating film formed at a site far from the counter electrode. A heat flow of the first electrodeposition coating film is performed, and then, in the second electrodeposition tank, a DC voltage is applied between the object to be coated and the counter electrode to form a second electrodeposition film on the object to be coated. In the electrodeposition coating method in which the first electrodeposition coating film and the second electrodeposition coating film are heat-cured after washing with water,
After washing of the article on which the first electrodeposition coating film has been formed, washing of the washing water stagnation surface which is substantially horizontal of the article to be washed in which washing water for washing is stagnant before the heat flow It is characterized by removing or reducing water.

  According to this method, the washing water on the stagnation surface of the article to be coated is removed or reduced after washing the article on which the first electrodeposition coating film has been formed and before the heat flow. When the first electrodeposition coating film on the outer surface of the coating is heat-flowed, a concave portion is hardly formed on the surface of the first electrodeposition coating film. The removal or reduction of the washing water is preferably performed without heating or in a low-temperature atmosphere so as not to cause an unintended heat flow of the first electrodeposition coating film.

  Here, even if the cleaning water on the stagnation surface of the cleaning water is not completely removed and remains partially, the remaining amount of the cleaning water is small, so when the heat flow of the first electrodeposition coating film, The washing water quickly evaporates by heating for the heat flow. That is, during heat flow, a state in which the volume shrinkage difference between the wet part and the dry part of the first electrodeposition coating film is not long does not continue. Therefore, it is avoided that a concave portion is formed at the boundary between the wet portion and the dry portion, and even if a concave portion is generated, the concave portion is shallow, so that even if the second electrodeposition coating film is formed thereafter, it is large. It will not be uneven.

  In a preferred embodiment, in order to remove or reduce the washing water on the washing water stagnation surface, gas is blown onto the washing water stagnation surface so that the washing water is excluded from the washing water stagnation surface. The washing water on the washing water stagnation surface can be removed or reduced by spraying gas onto the washing water stagnation surface of the object to be coated. It is preferable that the blowing speed of the gas with respect to the washing water stagnation surface is 20 to 25 m / sec. In this case, the spraying speed is the gas at a position where it is assumed that there is a stagnation surface of the washing water when the object is provided when the gas is sent in a state where the object is not provided. The flow rate of This also applies to the “blasting speed” of warm air described later.

  In a preferred embodiment, as the water washing of the article on which the first electrodeposition coating film is formed, dip water washing in which the article is immersed in washing water stored in a dip washing tank, and On the other hand, spray washing with spraying washing water is performed.

The apparatus for promoting washing water removal of the electrodeposition coating line disclosed herein is an apparatus used directly for carrying out the electrodeposition coating method for removing or reducing the washing water on the stagnant surface of the washing water before the heat flow described above,
In the first electrodeposition tank, a DC voltage is applied between the object to be coated and the counter electrode to form a first electrodeposition coating film on the object to be coated, and after washing the object to be coated, the counter electrode of the object to be coated Heat flow of the first electrodeposition coating film so that the electric resistance of the first electrodeposition coating film formed at a site close to is higher than the electric resistance of the first electrodeposition coating film formed at a site far from the counter electrode Then, in the second electrodeposition tank, a DC voltage is applied between the object to be coated and the counter electrode to form a second electrodeposition coating film on the object to be coated. A water washing station for washing the article on which the first electrodeposition coating film has been formed in the electrodeposition coating line in which the first electrodeposition coating film and the second electrodeposition coating film are heated and cured, and the first electrodeposition coating. It is installed between the heat flow stations that heat the coating film,
A means is provided for removing or reducing the washing water remaining after washing of the coating object from the flush water stagnation surface of the coating object where the washing water for washing is stagnant.

  According to this apparatus, since the washing water on the washing water stagnant surface of the object to be coated can be removed or reduced, when the first electrodeposition coating film on the outer surface of the object to be coated is heat-flowed, It becomes difficult to form a recess on the surface of the coated film. Therefore, even if a 2nd electrodeposition coating film is formed after that, it does not become a large unevenness | corrugation.

  In a preferred embodiment, as a means for removing or reducing the washing water from the washing water stagnation surface, a blow nozzle that blows gas to the washing water stagnation surface is provided so that the washing water is excluded from the washing water stagnation surface. .

  In a preferred embodiment, as the means for washing the article on which the first electrodeposition coating film is formed, a dip washing tank storing washing water for immersing the article to be coated, and washing the article to be coated And a spray nozzle for spraying water.

  In the electrodeposition coating method and the apparatus for promoting washing water removal in an electrodeposition coating line, the object to be coated can be, for example, an automobile body. In the case of an automobile body, for example, the roof serves as the washing water stagnation surface.

In the preferred embodiment of the apparatus for promoting removal of washing water in the electrodeposition coating line when the object to be coated is an automobile body, the washing water stagnation surface is a roof of the automobile body, and the blow nozzle is provided,
A guide rail extending from the washing station to the thermal flow station;
A hanger suspended from the guide rail and carrying the automobile body and transported from the washing station to the heat flow station,
The blow nozzle is arranged above the place where the automobile body is mounted on the hanger and passes through, with the gas outlet facing downward so that the gas is blown to the roof of the automobile body,
A solenoid valve for controlling the supply of gas to the blow nozzle and its stop;
The gas is supplied to the blow nozzle while the roof of the automobile body passes in front of the gas outlet of the blow nozzle, and the frame constituting the hanger crosses the front of the blow nozzle of the blow nozzle. And a control device for controlling the operation of the electromagnetic valve in accordance with the transport position of the automobile body so that the supply of gas is stopped.

  According to the apparatus for promoting washing water removal in this electrodeposition coating line, the washing water on the roof, which is the washing water stagnation surface, is blown into the gas while the automobile body is mounted on the hanger and transferred from the washing station to the heat flow station. It can be removed or reduced by attaching. When the frame constituting the hanger crosses the front of the gas outlet of the blow nozzle, the supply of the gas is stopped, so that foreign matter such as dust or oil that may have adhered to the frame is blown off by the gas and covered. Adherence to paint is avoided.

  Only one blow nozzle may be provided above the hanger, or a plurality of blow nozzles may be disposed above the hanger.

  In the electrodeposition coating method and the apparatus for promoting washing water removal of the electrodeposition coating line, in a preferred embodiment, the heat flow of the first electrodeposition coating film is determined by the baking temperature (150 ° C. to 180 ° C.) of the first electrodeposition coating film. C.) by blowing hot air having a temperature lower than that on the object to be coated. Since it is not heating by radiation but heating by warm air, even if cleaning water remains on the surface of the first electrodeposition coating film, the cleaning water is quickly removed. This is advantageous in preventing the formation of recesses on the surface.

  Here, the heat flow of the first electrodeposition coating film is such that, for example, the first electrodeposition coating film formed at a site close to the counter electrode of the object to be coated in the first electrodeposition tank has a temperature of 70 ° C. to 110 ° C. It is preferable to carry out the process so that it is heated for several minutes. When the heating temperature is low or when the heating time is short, the heat flow of the first electrodeposition coating near the counter electrode of the object to be coated becomes insufficient, and the electrical resistance does not increase sufficiently. This is disadvantageous in forming a second electrodeposition coating film having a desired thickness at a site far from the counter electrode of the object. On the other hand, when the heating temperature is high, or when the heating time is long, the first electrodeposition coating film that is thinly formed at a site far from the counter electrode of the object to be coated flows into a dense coating film, that is, The electrical resistance becomes high, which is disadvantageous for the formation of the second electrodeposition coating film on this far site.

  As described above, according to the present invention, after washing the coated object on which the first electrodeposition coating film is formed, before the first electrodeposition coating film is heat-flowed, the coating object is substantially horizontal. Since the cleaning water on the stagnant cleaning water surface is removed or reduced, it is avoided that a deep recess is formed on the surface of the first electrodeposition coating film due to a partial volume shrinkage difference of the first electrodeposition coating film during heat flow. As a result, even when the second electrodeposition coating film is formed thereon, and even when the intermediate coating film and the top coating film are formed, it is avoided that large unevenness is generated, and each part of the article to be coated is avoided. This is advantageous in improving the appearance of the coated object while forming an electrodeposition coating film having a desired thickness.

The figure which shows the electrodeposition coating line which concerns on embodiment of this invention. Sectional drawing which shows a 1st electrodeposition tank typically. The front view made into the partial cross section which shows a washing water removal promotion apparatus (air blow apparatus). The side view of the apparatus. The top view of the apparatus. The cross-sectional view of a coating-film heat flow apparatus. The longitudinal cross-sectional view of the same apparatus. Explanatory drawing of producing an unevenness | corrugation in an electrodeposition coating film.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. The following description of the preferred embodiments is merely exemplary in nature and is not intended to limit the invention, its application, or its use.

<Configuration of electrodeposition coating line>
The object to be coated on the electrodeposition coating line shown in FIG. In this electrodeposition coating line, a first electrodeposition station 2, a first water washing station 3, a washing water removal station 4, a heat flow station 5, a second electrodeposition station 6 and a second water washing station 7 are arranged in this order from the upstream side. Arranged. Although not shown, an electrodeposition coating baking station is provided next to the second washing station 7. The automobile body 1 is suspended on a hanger and sent to the stations 2 to 7 in order.

  The first electrodeposition station 2 is provided with a first electrodeposition tank 11 storing an electrodeposition paint into which the automobile body 1 subjected to chemical conversion treatment is immersed. In the first electrodeposition station 2, as shown in FIG. 2, cationic electrodeposition coating is performed using the automobile body 1 as a cathode and the counter electrode 10 provided in the first electrodeposition tank 11 as an anode. In addition, although the vehicle body 1 is conveyed with the hanger type conveying apparatus mentioned later and immersed in the electrodeposition coating material 9 with a hanger, illustration of a conveying apparatus is abbreviate | omitted in FIG.

  In the 1st water washing station 3, the dip water washing of the motor vehicle body 1 which the coating material of the 1st electrodeposition tank 11 electrodeposited, and the spray water washing following this are performed. For this purpose, a dip washing tank 12 and a spray nozzle 13 are provided. The automobile body 1 is washed by immersing it in washing water stored in the dip washing tank 12, and then washed with spray water sprayed by the spray nozzle 13.

  As the washing water for the dip washing and spray washing, a UF filtrate obtained by ultrafiltration (hereinafter sometimes referred to as “UF”) of the electrodeposition paint in the first electrodeposition tank 11 is used. For this purpose, a UF device 14 and a filtrate tank 15 for storing UF filtrate obtained by the UF device 14 are provided. In order to reduce the loss of the electrodeposition paint, the UF filtrate in the filtrate tank 15 is supplied to the spray nozzle 13, the sprayed cleaning liquid is collected in the dip washing tank 12, and the overflow water from the dip washing tank 12 is discharged to the first electric It is collected in the arrival tank 11.

  In the washing water removal station 4, the washing water of the roof, which is a substantially horizontal washing water stagnation surface where the washing water for washing the automobile body 1 stagnates, is forcibly removed or reduced without heating. In order to remove or reduce the washing water, a washing water removal promoting device 8 is provided. The station will be described in detail later.

  In the heat flow station 5, the first electrodeposition coating film formed on the outer surface of the automobile body 1 near the counter electrode of the first electrodeposition tank 11 heats, and the first electrodeposition coating film on the near portion is heated. The vehicle body 1 is heated so that the electrical resistance is higher than the electrical resistance of the first electrodeposition coating film formed at a site far from the counter electrode of the first electrodeposition tank 11 such as the inner plate portion of the vehicle body 1. For this purpose, a coating film heat flow device 16 is provided. The coating film heat flow device 16 includes a hot air heating furnace 17 to which hot air from a heater 18 is supplied. While the automobile body 1 passes through the hot air heating furnace 17, the first electrodeposition coating film is caused to heat flow. The specific configuration of the coating film heat flow device 16 will be described in detail later.

  The second electrodeposition station 6 is provided with a second electrodeposition tank 21 similar to the first electrodeposition tank 11 storing an electrodeposition paint into which the automobile body 1 that has passed through the heat flow station 5 is immersed. Also in the second electrodeposition station 2, cationic electrodeposition coating is performed using the automobile body 1 as an anode and a counter electrode (not shown) provided in the second electrodeposition tank 21 as a cathode. The electrodeposition paint of the second electrodeposition tank 21 of this example is the same in composition as the electrodeposition paint of the first electrodeposition tank 11, but the paint components of both electrodeposition tanks 11 and 21 are different. May be.

  In the second water washing station 7, spray water washing, dip water washing, spray water washing, dip water washing, and spray water washing of the automobile body 1 on which the paint of the second electrodeposition tank 21 is electrodeposited are sequentially performed. Therefore, the 1st-3rd spray nozzles 22-24, the 1st dip water washing tank 25, the 4th spray nozzle 26, the 2nd dip water washing tank 27, and the 5th spray nozzle 28 are provided.

  In the spray water washing by the first to fourth spray nozzles 22 to 24 and 26 and the dip water washing by the first dip water washing tank 25, UF obtained by ultrafiltration of the electrodeposition paint in the second electrodeposition tank 21 as washing water The filtrate is used. For this purpose, a UF device 31 and a filtrate tank 32 for storing the UF filtrate obtained by the UF device 31 are provided. In addition, cleaning liquid recovery tanks 33 and 34 for recovering the cleaning liquid sprayed by the second spray nozzle 23 and the third spray nozzle 24 are provided. On the other hand, industrial water is used for dip rinsing by the second dip rinsing tank 27 and spray rinsing by the fifth spray nozzle 28.

  In order to reduce the loss of the electrodeposition paint, the UF filtrate in the filtrate tank 32 is supplied to the first and fourth spray nozzles 22 and 26. The cleaning liquid sprayed by the fourth spray nozzle 26 is collected in the first dip water washing tank 25. The overflow water from the first dip rinsing tank 25 is recovered in the cleaning liquid recovery tank 34 for the third spray nozzle 24. The cleaning liquid in the cleaning liquid recovery tank 34 is supplied to the third spray nozzle 24, and the overflow water from the cleaning liquid recovery tank 34 is recovered in the cleaning liquid recovery tank 33 for the second spray nozzle 23. The cleaning liquid in the cleaning liquid recovery tank 33 is supplied to the second spray nozzle 23, and the overflow water from the cleaning liquid recovery tank 33 is recovered in the second electrodeposition tank 21.

<Washing water removal station 4>
The automobile body 1 is conveyed through the entire coating line including the washing water removal station 4 by an overhead conveyor (a hanger type conveying device). As shown in a simplified manner in FIGS. 3 and 4, the transport device includes a guide rail 41 extending along the painting line, and before and after moving along the guide rail 41 by engaging the guide rail 41 with a roller 42. Trolleys 43 and 44, and hangers 45 that are suspended from the trolleys 43 and 44 and on which the automobile body 1 is mounted. In FIG. 3, 49 is an oil pan.

  The hanger 45 includes front and rear portal frames 47 and 48 suspended from the front and rear trolleys 43 and 44 via C-neck 46 for supporting the automobile body 1 from both sides. The front and rear portal frames 47 and 48 are connected by connecting bars 51 and 52. Receiving portions 53 and 54 for receiving the automobile body 1 are provided at lower ends of the front and rear portal frames 47 and 48.

  In the present embodiment, the cleaning water removal promoting device 8 of the cleaning water removing station 4 is configured by an air blowing device that blows air as a gas toward the roof. As shown in FIG. 5, the air blowing device includes three sets, that is, a total of six nozzle mounting pipes 55, which are two sets. That is, two sets of left and right nozzle mounting pipes 55 arranged at intervals in the horizontal direction orthogonal to the conveyance direction of the automobile body 1 form one set, and the three sets are the front, middle and rear in the conveyance direction. They are lined up side by side. The nozzles 60 attached to the left and right nozzle attachment pipes 55 are responsible for the removal of the washing water at the left and right parts of the roof 1a.

  The nozzle mounting tube 55 is disposed above the place where the automobile body is mounted on the hanger 45 and passes. Each nozzle attachment tube 55 includes three nozzle attachment portions. In this embodiment, as shown in FIG. 3, the nozzle 60 is attached to one nozzle attachment portion via a copper tube 60a. Each nozzle 60 has an air outlet opening downward so that air is blown onto the roof 1 a of the automobile body 1. As indicated by arrows in FIG. 4, in the present embodiment, air blown from the nozzle 60 is blown toward the roof 1 a from above the portal frames 47 and 48 of the hanger 45. The blowing speed of the air with respect to the roof 1a is about 20-25 m / sec.

  Next, air piping for supplying air to the nozzle 60 will be described. A first air supply pipe 56 extends from an air compressor (not shown) as an air source alongside the vehicle body conveyance path in the cleaning water removal station 4. The first air supply pipe 56 branches into three second air supply pipes 57 to 59 so as to supply air to the three sets of nozzle mounting pipes 55. Each of the second air supply pipes 57 to 59 is branched into third air supply pipes 57a to 59a and 57b to 59b in order to supply air to the left and right nozzle mounting pipes 55.

  The first air supply pipe 56 is provided with a manual on-off valve 61 and an air pressure meter 62. Each of the three second air supply pipes 57 to 59 is provided with a manual open / close valve 63 for the pipe line, an electromagnetic valve 64 for controlling the supply and stop of air to the nozzle 60, and a pneumatic meter 65. .

  Thus, in the air blow device 8, air is supplied to the nozzle 60 while the roof 1 a of the automobile body 1 passes in front of the air outlet of the nozzle 60, and the portal frames 47 and 48 of the hanger 45 are connected to the nozzle 60. A control device 66 is provided for controlling the operation of the electromagnetic valve 64 in accordance with the transport position of the automobile body 1 so that the supply of air stops when crossing the front of the air outlet. For this control, an optical sensor (not shown) for detecting whether or not the roof 1a of the automobile body 1 passes in front of the air outlet of the nozzle 60 is provided, and the detection signal of the sensor is the control device. Given to.

<Heat flow station 5>
As shown in FIG. 6, the opposite side walls of the hot air heating furnace 17 have a double wall structure including an inner wall 71 and an outer wall 72. A tunnel furnace surrounded by an inner wall 71, a ceiling wall 73, and a bottom wall 74 is formed, and a guide rail 41 of a hanger type conveying device passes through the upper part of the tunnel furnace in the tunnel longitudinal direction. The automobile body 1 is mounted on the hanger 45 and passes through the tunnel furnace.

  Between the inner wall 71 and the outer wall 72 of the tunnel furnace, a hot air blowing means 76 including a heater, a blower motor and a blower fan is provided. Thus, the upper, middle, and lower nozzle boxes 77, 78, and 79 for blowing warm air toward the automobile body 1 mounted on the hanger 45 are provided on the opposed inner side walls 71.

  As shown in FIG. 7, each of the middle and lower nozzle boxes 78, 79 has a plurality of longitudinally slotted first hot air outlets 81 that blow out hot air toward the side surface of the automobile body 1 at intervals in the tunnel longitudinal direction. Prepared. The upper nozzle box 77 includes a second hot air outlet 82 in the form of a cylindrical hole that blows out hot air toward the roof 1 a that is the stagnation surface of the washing body of the automobile body 1.

  Here, the distance from the second hot air outlet 82 to the roof 1a is farther than the distance from the first hot air outlet 81 to the side surface of the automobile body 1. Therefore, the hot air blowing speed of the second hot air outlet 82 is set higher than the hot air blowing speed of the first hot air outlet 81 so that the hot air reliably reaches the roof 1a. Moreover, in order to improve the directivity of warm air, the 2nd warm air blower outlet 82 is formed in the cylinder hole shape. The blowing speed of the warm air to the body side surface and the roof 1a of each of the first warm air outlet 81 and the second warm air outlet 82 is about 5 to 15 m / sec.

  An air suction port 83 for sucking the heated air in the tunnel furnace and circulating it to the hot air blowing means 76 is opened at the upper part of the inner wall 71.

<Electrodeposition coating>
In the first electrodeposition station 2, as shown in FIG. 2, the automobile body 1 is immersed in the electrodeposition paint 9 in the first electrodeposition tank 11. Thereby, a 1st electrodeposition coating film is formed in the outer-plate part and inner-plate part of the motor vehicle body 1. FIG. The first electrodeposition coating film is formed thick at a portion where the current density is close to the counter electrode 10 like the outer plate portion, and is thinly formed at a portion where the current density is far from the counter electrode 10 like the inner plate portion. The

  The automobile body 1 is conveyed from the first electrodeposition station 2 to the first water washing station 3 while being mounted on the hanger 45. In the first water washing station 3, the automobile body 1 is dipped in water by being dipped in the washing water of the dip water washing tank 12 and pulled up, and then spray water washing is performed by spraying the washing water by the spray nozzle 13. .

  The automobile body 1 is transported from the first washing station 3 to the washing water removal station 4 while being mounted on the hanger 45. In the washing water removal station 4, when the roof 1a of the automobile body 1 passes in front of the air outlet of each nozzle 60, the electromagnetic valve 64 related to the nozzle 60 is opened and air is blown onto the roof 1a. By this air blowing, most of the wash water stagnating in the room 1a is blown off and removed. Therefore, it is advantageous in preventing the first electrodeposition coating film from forming recesses in the subsequent heat flow step. Further, when the frames 47 and 48 of the hanger 45 pass in front of the air outlet of the nozzle 60, the blowing of air stops. Accordingly, it is possible to avoid the oil and dust adhering to the hanger 45 being blown away by air and adhering to the first electrodeposition coating film.

  The automobile body 1 is conveyed from the washing water removal station 4 to the heat flow station 5 while being mounted on the hanger 45, and is carried into the hot air heating furnace 17, that is, into the tunnel furnace. The first electrodeposition coating on the outer plate portion of the automobile body 1 is heated by the hot air blown out from the first hot air outlet 81 and the second hot air outlet 82 while passing through the tunnel furnace, and heat flows. .

  Since the warm air from the second warm air outlet 82 is directed to the roof 1a, even if the washing water remains on the roof 1a, the washing water quickly evaporates. That is, the boundary between the portion of the roof 1a that has been removed with the washing water and the dry portion disappears quickly. Therefore, the temperature of the first electrodeposition coating film rises substantially uniformly over the entire surface of the roof 1a. Therefore, it can be avoided that a portion having a different volume shrinkage is generated in the first electrodeposition coating film, and a local recess is formed.

  Since the warm air from the first and second warm air outlets 81 and 82 is applied to the outer plate portion of the automobile body 1, the first electrodeposition coating film on the outer plate portion heat-flows, but the first electric power on the inner plate portion. The amount of heat received by the coating film is small. For this reason, the first electrodeposition coating film on the inner plate portion has a lighter heat flow than the first electrodeposition coating film on the outer plate portion. When viewed from the outer plate, there is almost no heat flow at the deep part of the inner plate. Therefore, the electrical resistance of the first electrodeposition coating film on the outer plate portion is higher than that of the first electrodeposition coating film on the inner plate portion.

  The automobile body 1 is conveyed from the heat flow station 5 to the second electrodeposition station 6 while being mounted on the hanger 45. At the second electrodeposition station 6, the automobile body 1 is immersed in the electrodeposition paint of the second electrodeposition tank 21. Thereby, a 2nd electrodeposition coating film is formed in the outer-plate part and inner-plate part of the motor vehicle body 1. FIG. In this case, due to the previous heat flow, the first electrodeposition coating film on the outer plate portion has a higher electrical resistance than the first electrodeposition coating film on the inner plate portion. A large amount of the electrodeposition paint of the second electrodeposition tank 21 adheres to the part. Therefore, by adjusting the immersion time of the automobile body 1 in the electrodeposition paint in the second electrodeposition tank 21, the thickness of the electrodeposition coating on the outer plate portion and the inner plate portion (the first electrodeposition coating film and the first electrodeposition coating film) is adjusted. It is easy to control the thickness of the two electrodeposition coating films to a desired film thickness.

  The automobile body 1 is transported from the second electrodeposition station 6 to the second washing station 7 while being mounted on the hanger 45. In the second water washing station 7, the car body 1 is sprayed with the first to third spray nozzles 22 to 24, dip water washed with the first dip water washing tank 25, spray water washed with the fourth spray nozzle 26, second Dip water washing by the dip water washing tank 27 and spray water washing by the fifth spray nozzle 28 are sequentially performed.

  The automobile body 1 is transported from the second washing station 7 to the electrodeposition coating baking station while being mounted on the hanger 45, and the first electrodeposition coating and the second electrodeposition coating are baked and cured.

<Others>
As a hanger for conveying an automobile body, a C-type hanger that supports the automobile body 1 from one side thereof can also be adopted. In this case, in the washing water removal station 4, the second air supply pipes 57 to 59 are arranged on the opposite side of the C-type hanger across the vehicle body 1, and the second air supply pipes 57 to 59 are connected to the C-type hanger. The air supply pipe can be extended toward an intermediate position between the position where the upper frame passes and the position where the roof 1a of the automobile body 1 passes, and the nozzle 60 can be arranged at the intermediate position. Thereby, since the upper frame of a hanger does not pass under the nozzle 60, when the roof 1a passes under the nozzle 60, air can be continuously sprayed with respect to the room 1a.

  When the C-type hanger is adopted, the position where the upper frame of the C-type hanger passes and the position where the roof 1a of the car body 1 passes from the opposite side of the C-type hanger across the car body 1 also in the heat flow station A hot air blowing pipe can be extended at an intermediate position. Thereby, since the 2nd warm air blower outlet 82 can be arrange | positioned below right above the position where the roof 1a passes, it becomes advantageous when evaporating and removing the washing water remaining on the roof 1a quickly.

  In the above embodiment, the first electrodeposition paint and the second electrodeposition paint have the same composition, but an electrodeposition paint having a composition different from that of the first electrodeposition paint can be adopted as the second electrodeposition paint. .

1 Auto Body (Coating)
1a Roof (wash water stagnation surface)
2 First Electrodeposition Station 3 First Washing Station 4 Washing Water Removal Station 5 Heat Flow Station 6 Second Electrodeposition Station 8 Washing Water Removal Promotion Device (Air Blow Device)
DESCRIPTION OF SYMBOLS 9 Electrodeposition coating 10 Counter electrode 11 1st electrodeposition tank 12 Dip washing tank 13 Spray nozzle 16 Coating-film heat flow apparatus 17 Hot air heating furnace 45 Hanger 47 Frame 48 Frame 55 Nozzle attachment pipe 60 Nozzle 71 Side wall 76 Hot air blowing means 81 First hot air outlet 82 Second hot air outlet

Claims (11)

In the first electrodeposition tank, a DC voltage is applied between the object to be coated and the counter electrode to form a first electrodeposition coating film on the object to be coated, and after washing the object to be coated, the counter electrode of the object to be coated Heat flow of the first electrodeposition coating film so that the electric resistance of the first electrodeposition coating film formed at a site close to is higher than the electric resistance of the first electrodeposition coating film formed at a site far from the counter electrode Then, in the second electrodeposition tank, a DC voltage is applied between the object to be coated and the counter electrode to form a second electrodeposition coating film on the object to be coated. In the electrodeposition coating method in which the first electrodeposition coating film and the second electrodeposition coating film are cured by heating,
After washing of the article on which the first electrodeposition coating film has been formed, washing of the washing water stagnation surface which is substantially horizontal of the article to be washed in which washing water for washing is stagnant before the heat flow An electrodeposition coating method characterized by removing or reducing water. In claim 1,
The removal or reduction of the washing water on the washing water stagnation surface is characterized by spraying a gas onto the washing water stagnation surface so that the washing water is excluded from the washing water stagnation surface. In claim 1 or claim 2,
As rinsing of the object to be coated on which the first electrodeposition coating film has been formed, dip rinsing in which the object is immersed in rinsing water stored in a dip rinsing tank, and washing water for the object to be coated An electrodeposition coating method comprising spray spray washing and spraying. In any one of Claim 1 thru | or 3,
The heat flow of the first electrodeposition coating film is performed by blowing hot air having a temperature lower than the baking temperature of the first electrodeposition coating film onto the object to be coated. In claim 4,
The heat flow of the first electrodeposition coating film is such that the first electrodeposition coating film formed at a position close to the counter electrode of the object to be coated in the first electrodeposition tank has a temperature of 70 ° C. to 110 ° C. for several minutes. An electrodeposition coating method characterized by being performed in a heated state. In any one of Claims 1 thru | or 5,
The electrodeposition coating method, wherein the object to be coated is an automobile body, and the washing water stagnation surface is a roof of the automobile body. In the first electrodeposition tank, a DC voltage is applied between the object to be coated and the counter electrode to form a first electrodeposition coating film on the object to be coated, and after washing the object to be coated, the counter electrode of the object to be coated Heat flow of the first electrodeposition coating film so that the electric resistance of the first electrodeposition coating film formed at a site close to is higher than the electric resistance of the first electrodeposition coating film formed at a site far from the counter electrode Then, in the second electrodeposition tank, a DC voltage is applied between the object to be coated and the counter electrode to form a second electrodeposition coating film on the object to be coated. A water washing station for washing the article on which the first electrodeposition coating film has been formed in the electrodeposition coating line in which the first electrodeposition coating film and the second electrodeposition coating film are heated and cured, and the first electrodeposition coating. It is installed between the heat flow stations that heat the coating film,
A means for removing or reducing washing water remaining after washing of the coating object from a substantially horizontal washing water stagnation surface of the coating object where washing water for washing is stagnant is provided. Cleaning water removal promotion device for the coating line. In claim 7,
As a means for removing or reducing washing water from the washing water stagnation surface, a blow nozzle that blows gas to the washing water stagnation surface is provided so that washing water is excluded from the washing water stagnation surface. Cleaning water removal promotion device for electrodeposition coating line. In claim 7 or claim 8,
As a means for rinsing the object on which the first electrodeposition coating film is formed, a dip rinsing tank storing washing water for immersing the object to be coated, and a spray nozzle for spraying the washing water on the object to be coated And an apparatus for promoting washing water removal in an electrodeposition coating line. In any one of Claims 7 to 9,
For heat flow of the first electrodeposition coating film, a heat flow device is provided that blows hot air having a temperature lower than the baking temperature of the first electrodeposition coating film on the object to be coated. Cleaning water removal promotion device for electrodeposition coating line. In claim 8, claim 9 quoting claim 8, or claim 10 quoting claim 8,
The article to be coated is an automobile body, the washing water stagnation surface is a roof of the automobile body,
A guide rail extending from the washing station to the thermal flow station;
A hanger suspended from the guide rail and carrying the automobile body and transported from the washing station to the heat flow station,
The blow nozzle is arranged above the place where the automobile body is mounted on the hanger and passes through, with the gas outlet facing downward so that the gas is blown to the roof of the automobile body,
A solenoid valve for controlling the supply of gas to the blow nozzle and its stop;
The gas is supplied to the blow nozzle while the roof of the automobile body passes in front of the gas outlet of the blow nozzle, and the frame constituting the hanger crosses the front of the blow nozzle of the blow nozzle. A cleaning water removal accelerating device for an electrodeposition coating line, comprising: a control device that controls the operation of the electromagnetic valve in accordance with the transport position of the automobile body so that gas supply is stopped.

Images